Efficient and safe gas turbine engine operation requires pressure ratios to be below the operating limit lines of the compressor. Specifically, pressure ratios greater than the operating limit lines may result in compressor surge and the like. Higher pressure ratios may arise in applications where, for example, low BTU fuels or fuels with diluent injections are used and/or at cold ambient temperature conditions. The compressor pressure ratio typically may be larger than the turbine pressure ratio in that the turbine pressure ratio may be subject to pressure losses in the combustor. Compressor surge and the like may cause significant damage and resultant gas turbine engine downtime.
A common solution for compressor pressure ratio protection is the bleeding off of gas turbine compressor discharge air and recirculating the bleed air back to the compressor inlet. Such inlet bleed heat control raises the inlet temperature of the compressor inlet air by mixing the colder ambient air with the bleed portion of the hot compressor discharge air, thereby reducing the air density and the mass flow to the gas turbine.
Current inlet bleed heat manifolds, however, may be sized such that a minimum flow rate is required for even flow distribution. As a result, the minimum bleed heat flow may be in excess of the required flow rate for operating limit line protection and/or anti-icing protection. The use of such a minimum bleed heat flow in excess of actual requirements thus may result in a loss of gas turbine output, heat rate, and efficiency.